Created attachment 134236 [details]
Video showing the issue

SUMMARY


STEPS TO REPRODUCE
1. Open any CSD window (in this case I tested using Firefox and Gnome Chess)
2. Maximize window to see problem clearly (it also happens on non-maximized windows, this step is just to make it easier to see the problem)
3. Hover over the close/maximize/minimize buttons
4. Now check any SSD windows, the hitbox for highlighting the buttons is different

OBSERVED RESULT

The button hitbox is smaller/different from any other Server Side Decoration windows. Like, in a normal maximized window, one can close the window by clicking on the top right pixel of the screen, however on CSD windows, in order to highlight the button, the user has to precisely target the button. I'm no UX expert, but I believe that breaks Fitts law.

I've attached a video showing the issue.

EXPECTED RESULT


Operating System: KDE neon Unstable Edition
KDE Plasma Version: 5.20.80
KDE Frameworks Version: 5.78.0
Qt Version: 5.15.2
Kernel Version: 5.4.0-58-generic
OS Type: 64-bit
Processors: 6 × Intel® Core™ i5-9400F CPU @ 2.90GHz
Memory: 7.7 GiB of RAM
Graphics Processor: Radeon RX 570 Series

ADDITIONAL INFORMATION

KDE NEON Unstable fully updated - Dec 20 2020